The present invention relates to the field of air treatment devices for warming and circulating the air in the passenger compartment of an automobile or other automotive vehicle, and more particularly relates to such an air treatment device which is capable of operating in a bilevel mode, in which generally warmer air is supplied to the feet regions of a person in the front seat of the automobile, and generally cooler air is supplied to such a person's upper body regions.
Various air treatment devices for automobiles are well known. The simplest such device consists of merely a heater element mounted within the passenger compartment of the automobile, and a blower which blows air through this heater element to be circulated within the passenger compartment. As a more sophisticated type, air duct systems may be provided for directing the air flow from a blower (the effect of which may alternatively be provided by a ram air effect from the outside of the automobile, when it is moving), so as to make said air flows pass through the heater and then through various ducts which lead to different parts of the interior of the automobile, such as defroster ducts which direct heated air to the windshield for removing accumulations of frost and ice in very cold weather, foot warming ducts for directing hot air onto the feet of people in the front and sometimes also in the rear seats of the vehicle, and the like.
From the ergonomic point of view, it has been noted that human beings confined within a cramped space such as the interior of an automobile are most comfortable, with regard to circulation of treated air, when their lower body portions such as their feet are kept warmer than their upper body portions such as their heads. Thus, a demand has arisen for an air treatment assembly which provides a so called bilevel mode, in which warmed air is blown towards the lower body portion, i.e., the feet, of a person sitting in the driver's or the passenger's seat of the automobile, and substantially cooler air, perhaps almost entirely unheated air, is blown towards the upper body portion, i.e., the head, of such a person. It is also of course desirable, in view of the wide diversity of weather conditions in which an automobile may be expected to be used, that the temperature of both of these air streams, the difference between the temperatures of these air streams, and the flow rates of these air streams, should also be individually and independently adjustable. It is also a desirable design characteristic for such an air treatment assembly to incorporate only one blowing means such as a blower motor, and for said air treatment assembly to be as simple as possible without the provision of a large number of air flaps and dampers for regulating the flow of air to the various portions thereof, because the operator of an automobile is not likely to spend a great deal of trouble in order to understand the precise operation of a complicated air treatment system, and accordingly, if an air treatment system is unduly complex and is equipped with too many controls, it will probably not be operated so as to give the best results with regard to air circulation.
Therefore, a prior art air treatment assembly has been proposed and practiced, constructed generally as follows. An air duct, into which air is blown at an upstream end by a blower motor, or by a ram air effect when the vehicle is moving, or the like, has a heater element mounted across part of its cross sectional area. A movable damper has been mounted upstream of the heater element, said damper dividing the air flow passing into the air duct into a first air flow portion passing through the heater element, and a second air flow portion bypassing the heater element. Downstream of the heater element, a first air outlet and a second air outlet open from the air duct. The first air outlet, generally called the heater outlet, is for blowing air onto the lower body portion, i.e., the feet, of a person sitting in the driver's or the passenger's front seat of the automobile, and the second air outlet, generally called the vent outlet, is for blowing air to the upper part of the body, i.e., to the head, of such a person. Dampers are provided for selectively opening and closing the first and second air outlets. If properly constructed with proper arrangement of the shape of the air duct, and of the positions of the first and second air outlets therein, such an air treatment system is capable of providing three modes: (a) a heater mode, wherein warmed air is available, only from the first air outlet, towards the feet of a person sitting in the front seat of the vehicle; (b) a vent mode, wherein non-warmed air is available, only from the second air outlet, towards the head of a person sitting in the front seat of the vehicle; and (c) a bilevel mode, in which relatively warmer air is available from the first air outlet generally towards the feet of a person sitting in the front seat of the vehicle, and at the same time relatively cooler air is available from the second air outlet to be directed generally towards the head of such a person.
Such an operation is provided as follows.
First, if the aforesaid damper is set so as substantially to cut off said second air flow portion, so that substantially all of the air passing into the air duct passes through said heater element, then downstream of the intermediate portion of the air duct where the heater element is mounted, only relatively hot air will be available. In this condition, if the second air outlet, i.e. the vent outlet, is closed by selective operation of its damper, and the first air outlet, i.e. the heater outlet, is opened by selective operation of its damper, thereby the aforesaid heater mode will be obtained, wherein warm air is directed onto the feet portions of a person sitting in the front seat of the vehicle.
Next, if the aforesaid damper is put into its position wherein it substantially cuts off said first air flow portion, so that substantially no portion of the air directed into the air duct is passed through said heater element, and instead this air almost entirely bypasses the heater element, thereby downstream of the heater element only substantially cold air will be provided. If, in this condition, said first air outlet, i.e. the heater outlet, is substantially closed off by selective operation of its damper, and said second air outlet, i.e. the vent outlet, is opened up by selective operation of its damper, thereby the vent mode is attained, wherein substantially cool air is directed to the upper body portions or the head of a person sitting in the front seat of the vehicle, from the vent outlet.
Finally, if the aforesaid damper is placed in an intermediate position, wherein the air directed into the air duct is divided into approximately equal first and second air flow portions, the first air flow portion passing through said heater, and the second air flow portion bypassing said heater, and if both said first air outlet, i.e. the heater outlet, is opened, and also said second air outlet, i.e. the vent outlet, is opened, by proper selective operation of their dampers, then, if the configuration of the downstream portion of the air duct, and the positioning of the first and second air outlets therein, are properly arranged, then the first air flow, which has been warmed by passing through the heater, preferentially passes out through the first air outlet, i.e. the heater outlet, and the second air flow, which has not been warmed because it has bypassed the heater, preferentially passes out through the second, i.e. the vent, air outlet. This is possible because the mixing of the first and second air flows, downstream of the heater element, does not occur immediately, and with proper configuration of the shape of the portion of the air duct downstream of the heater, this mixing can be effectively precluded. In this condition, the so called bilevel mode is attained, wherein warm air is directed onto the lower body portions or the feet of the person in the front seat of the vehicle, and cooler air is directed to the upper body portions or the head of such a person. In other words, the so called head cold feet warm condition is obtained. Of course, some warming of the vent air from the second or vent air outlet, and some cooling of the heated air from the first or heater air outlet occurs, by mixing of the first and second air flow portions downstream of the heater, but this may in fact be beneficial to the comfort produced by such an air treatment assembly.
This sort of bilevel construction for an air treatment assembly has been reasonably successful in practice in providing a bilevel mode of operation in which the head cold feet warm condition for the driver is attained. However, it does not work completely perfectly, and also it lacks adjustability. The amount of mixing of the first and second air streams, i.e., more exactly, the proportions in which the air from the first or heater air outlet is composed of air from the first and second air flow portions, and the proportions in which the vent air from the second or vent air outlet is composed of air from the first and second air flow portions, are designed into the apparatus by the physical configurations of the air duct and the air outlets, and, with fixed flow rates of the first and second air streams, cannot be selectively varied by the operator of the vehicle. Further, in the bilevel mode, the difference between the temperature of the cooler air blown out through the second or vent outlet to the head of a person sitting in the front seat of the vehicle, and the temperature of the warmer air blown out through the first or heater outlet towards his feet, cannot be adjusted. Accordingly, since different vehicle operators have different requirements with regard to the intensity of the head cold feet warm condition which they prefer, a problem has arisen with regard to controllability.
Further, a problem has arisen with this prior art construction, in that, when it is operating in the non-bilevel mode, because the first air flow portion and the second air flow portion may not always properly mix downstream of the heater, a certain unevenness of the temperature of the air obtained from the first or heater air outlet, and from the second or vent air outlet, has sometimes undesirably occured.